Manufacturing apparatus and method for operating the same



y 1955 H. J. REINDL ETAL 3,181,502

MANUFACTURING APPARATUS AND METHOD FOR OPERATING THE SAME Filed March15, 1961 2 Sheets-Sheet 1 INVENTORfi HAROLD J. HEINDL CHARLES W. KILLENy 1965 H. J. REINDL ETAL 3,181,502

MANUFACTURING APPARATUS AND METHOD FOR OPERATING THE SAME Filed March15, 1961 2 Sheets-Sheet 2 4 INVENTORS a HAROLD J. REINIDL HARLES w.KlLLEN HEIR ATTORNEY United States Patent 3,131,502. MANUFACTURE???APPARATUS ANE METHLD FER @iERA'llNG TEE SAME Harold J. Reindl, Dayton,and Charles W. Killers, Piqua,

Ohio, assignors to General Motors Corporation, Betreit, Mich, acorporation of Delaware Filed Mar. 15, 196i, Ser. No. 5,986 2 (Ur. ltd-27) This invention relates to coating operations and is particularlyconcerned with electrostatic coating operations and apparatus forcarrying out the same.

The main object of the invention is to provide a new and improved methodand apparatus for coating articles with a coating material whereinelectrostatic forces are used in conjunction with moving air wherein theair transports the coating material in charged condition and to the partto be coated whereupon the electrostatic charges aid in depositionthereof.

In carrying out the above object, it is a further object to provide amethod for electrostatically depositing paint onto an article whereinpaint is supplied at a controlled rate through an electrostic chargingzone and thereafter is concentrated and subdivided by supplementalphysical forces for directing the charged paint and depositing the sameon the article.

Another object of the invention is to provide an apparatus for carryingout the above object wherein an air moving means is utilized forconcentrating charged paint material and for throwing the charged paintonwardly thereof in dispersed condition, means also being provided forsupplying additional air to said first air moving means for aiding inthe mechanical dispersion of the paint.

Another object of the invention is to utilize a squirrel cage blower asan air moving means and supplement the movement of air thereby throughthe use of additional air supply which provides additional air to theblower.

A still further object of the invention is to provide a second airmoving means below the first air moving means for creating a physicalmovement of air in a zone beneath the first mentioned air moving meanswhereby paint particles being distributed and dispersed by the first airmoving means are concentrated and the pattern thereof is modified.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being bad to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In t e drawings:

FIG. 1 is a perspective view partly in section showing one type ofapparatus with a diagrammatic electrical circuit therefor.

FIG. 2 is a view in section of another type of air moving means.

FIG. 2a is a perspective view of a modified supply device.

FIG. 3 is a view in section of a third type of air moving means.

FIG. 4 is a view in section of the device shown in FIG. 2 incorporatinga supplemental blower for controlling the pattern of paint depositionand FIG. 5 is a diagrammatic view showing the device of FIG. 4 inoperation wherein the paint pattern is depicted by dash lines onto thearticle to be coated.

In copending application Serial No. 710,665, now Patent Number2,976,175, filed January 23, 1958, a paint depositing method andapparatus are described. In this application a squirrel cage blower isused as a means for moving paint particles from the charging zone to theilhlfidz Fatented May 4i, i965 zone of deposition on the article. Thisapparatus operates efficiently and does a satisfactory job of depositingpaint electrostatically. In this apparatus, however, it is necessary tocontrol within rather precise limits the quantity of paint or othercoating material which is supplied to the device in order to obtainoptimum results. In other words, excessive power is required if thepaint is not fully broken up by the electrostatic and mechanical forces.

The present invention is directed to an improvement over the inventiondisclosed in said Patent 2,976,175. In the present invention the samesquirrel cage blower is used as an air moving means and a cup or supplydam is used as a means for supplying the paint thereto. However, thecritical nature of the paint supply is greatly lessened through the useof supplemental air moving means. Thus, by following the presentinvention it is possible to utilize a greater quantity of paint or othercoating material during the same time interval and with the same sizeblower mechanism and power source while obtaining a highly eflicientcoating operation wherein the particles of paint or other coatingmaterial are extremely small and uniform in size.

Specifically referring to FIG. 1, a motor Ed is shown which may beeither electric or air driven and which has a housing 22 depended andinsulated therefrom that is connected by wire 24 to one side of a powerpack 2d. The other side of the power pack 26 is connected by wire 28 toa conveyor 30 which carries an article 32 to be coated thereon by meansot a conductive hanger S4. The hanger is suitably covered or coated toprevent any substantial paint deposition thereon except for the areas ofcontact with the article.

The housing 22 acts as a journal for a motor shaft 34, that is alsoinsulated from the motor, when an electric motor is used, which carriesat its lower end a squirrel cage blower unit 36. Electrically connectedto the housing 22 and carried thereby is a shallow tray or paint supplyplate 33 which is circular in form and concentrically mounted upon thehousing 22. The plate has a rim 4t therearound preferably about /8 of aninch high which acts as a dam for paint or other coating materialsupplied to the plate 33. Fluid paint is supplied through a paint supplytube :2 from a paint source and only sulilcient pressure is supplied tothe paint to cause the desired rate of flow through the tube. As painton the plate 38 reaches the top of the dam 40 it overflows around thedam and drops into the interior of the squirrel cage rotor 35. In thisconnection it is preferable, but not necessary, that the plate beslightly above the top of the blower 36. If the plate is placed lowerand within the blower the only etfect will be to lessen the Width of thepaint throwing pattern.

Also mounted on the shaft 34' is a second and smaller squirrel cageblower M. The second blower 44 is preferably slightly less in diameterthan the outer diameter of the plate 38 so that it is shielded againstpaint dropping directly thereon. Similarly, the height of the rotor 44is preferably less than the height of the rotor as and the rotor dd ispreferably spaced equidistant from opposite end faces of the rotor 36.

As the two rotors are caused to rotate simultaneously the paint whichoverflows the dam ib drops in charged condition in between the tworotors, namely on the outside of the small rotor and on the inside ofthe large rotor. Furthermore, the paint is drawn inwardly into thisspace between the two rotors by suction since the bases of the tworotors are either solid or restricted while the top portions of the tworotors are fully open. It has been found that sufiicient paint may besupplied through the tube 42 to flow over the darn it in a film or sheetwherein the electrostatic forces alone are sufficient to disperse thepaint to any appreciable extent. However, due to the extreme turbulencebetween the two rotors and the considerable suction created thereby, thepaint, as it is drawn between the rotors, is thrown outwardly of rotor36 in a finely dispersed and fully charged condition wherein eachparticle of paint is charged and wherein the uniformity of size of thedispersed particles is extremely uniform and fine. These particles areobviously attracted to the article 32 which bears an opposite electricalcharge to the charge on the particles whereby the article becomes coatedwith the particles of coating material. Since the rotor produces a cloudof particles considerably wider than the article 32 the particlespassing the article 32 are drawn onto the surface thereof so thatconsiderable wrap around of coating material is obtained without any substantial loss thereof. In this connection, the width of the rotor 36 ischosen so that it will be substantially the same as the height of thearticle 32 or if the rotor 35 is narrower than the article the entirerotor assembly may be reciprocated vertically within the limits shown atthe arrow in FIG. 1 so that the upper and lower limit of the patternwill completely envelop the article. These deviations are well known inthe art.

Referring to FIG. 2, a modification of the device shown in FIG. 1 isillustrated. In this instance all of the parts of the device are thesame with respect to the motor, plate, and rotor 36. However, the shaft34 which carries the rotor 36 is hollow in this instance and isconnected to a suitable source of compressed air. This may be theexhaust of the motor, if the motor is air driven. In any event, theshaft 34 is apertured a plurality of times as at 50 and the air issuingfrom the apertures 50 is used to supplement the air stream created bythe blower 36. The apertures, therefore, act in much the same manner asdoes the supplemental rotor 44 as shown in FIG. 1.

A somewhat similar device is shown in FIG. 3. In this instance thehollow shaft 34' is used but includes apertures 52 at the base thereofthat connect through a bearing fitting 54 to ducts 56 in the fitting 54.Immediately above the ducts 56 is a flared shield 6% that preferablyrotates with the remainder of the device and which shields the plate 38from direct impingement of air from the ducts d thereon. The plate 3% isthe same as previously noted except that in this instance the plate ispositioned within the rotor 36. As previously mentioned this will reducethe height of the pattern slightly, however, due to the flow of the airfrom the ducts 56 as directed by the shield 69 there is a tendency forthe paint or other material coming off the dam 4-0 to be blown upwardlyso that the entire field is reasonably well covered. Here, again, thesupplemental air is used as a means for aiding in the conveyance andbreaking up of the coating material which flows over the dam 4t) andhere, again, a considerably greater quantity of material can be suppliedthan in the device as shown in said Patent 2,976,175.

FIG. 4 shows a device similar to that shown in FIG. 2 with the exceptionthat a second blower 7% is mounted on the same shaft which blower ispreferably smaller in diameter than the blower 36 and is mounted belowthe blower 36. The effect of this second blower is to create a definiteflow of air beneath the first blower whereby the tendency for paintparticles to drop downwardly is prevented. Generally speaking, in anydevice of this character the paint pattern at a distance from the blowerwill be wider than the blower and the excess width will be noted belowthe plane of the blower indicating a tendency for the coating particlesto drop slightly by gravity. By adding the second blower 7th, additionalair is supplied to supplement the normal movement of the particles andthereby overcome this gravitational pull.

The effect of the blower 70 is shown in FIG. 5 wherein a diagrammaticview is shown. In this instance the power pack is shown at 26 and thearticle to be painted at 32 whereas the dual blower arrangement is notedat d '75. The pattern is indicated by the dash lines and issubstantially the same width throughout its extent. In this instance arear shield '77 is provided which prevents painting from the back sideof the device wherein the paint which is thrown onto the shield isrecovered and returned to the paint supplythrough tube 79.

In connection with the rear shield 77, it is apparent that improvedaction maybe obtained by using a supply plate 33 which is a segment of acircle, for example or a semi-circular plate and dam 40. This may berotatably adjustable on the housing 22 so that a minimum of paint willbe directed against the shield 77.

We have also found that the electrical charge may be imposed on thepaint by several means other than using a charged plate 38. For example,the paint supply line, which is formed from a non-conducting material,may be broken as noted in FIG. 4, A tubular metal segment 99 is theninserted as a connector in the line. The segment 9t! is connected to oneside of the power pack and is the only connection thereto on the paintdistributor side of the device. The distance from the exit of the lineis not important, preferably from 6 to 18" from the exit. The paintingresults are not effected and satisfactory operation is obtained. Inplace of a metal tube Hi other conductors, such as a metal screen orconductive screw etc., placed within the non-conducting supply pipe maybe used. The conductive insert, of course, should be connected to oneside of the power pack. In each case the plate 355 will then merely actas a distributor.

in all of the embodiments shown in this application the criticality ofcontrol is greatly reduced. This may be explained by the fact that inthe device shown in application 710,665 the control of the paint supplymust be maintained so that substantial dispersion is obtained as thepaint runs off the distributing plate. This atomized or partiallyatomized paint is in a dispersed condition as it enters the blower andthe blower merely subdivides it into a finer dispersion and lendskinetic impetus and direction to the particles to enable them to bridgethe gap between the blower and the article to be painted. Thus, in eachinstance it is highly desirable to cause substantial dispersion of thecoating material from the plate. This, of course, limits the quantity ofcoating material which may be supplied to the plate and, similarly,limits the quantity of coating material that can be distributed by thedevice.

In the present instance this critical factor is substantially eliminatedand large quantities of paint may be supplied to the plate 33 wherein itis not necessary to break up any great amount of the paintelectrostatically since suflicient turbulence and air movement ispresent within the blower due to the supplemental air being suppliedthereto to effect dispersion of the paint particles whereby theelectrostatic forces are merely used as a charging means and are notdepended upon as a means for dispersing the paint. This condition iscreated by the conjoint action of the blower and the secondary airsupply means which not only disperses the paint into fine particles ofuniform size but likewise aids in transporting these par-- ticles acrossthe gap between the blower and the article to be painted hurling themwith substantial force onto the article to be painted. The electrostaticforces on the other hand are used for their ability to cause wrap aroundof particles that pass the article to be painted whereby the back sideof the article receives a substantial coating which is not possible whenthe electrostatic forces are not present. The electrostatic forces aloneare not sufiicient to cause deposition of any paint particles on thearticle until the air moving device is in operation, thus demonstratingthe conjoint action of the several forces to eifect efficient painting.

It is apparent that in place of the plate 38 and dam 443 that a ringtype manifold 38 as shown in FIG. 2a could be substituted therefor. Inthis case this manifold would be apertured with the apertures Preferablypointing in a downward direction and spraying the paint into the blower36. Any number of apertures could be used as desired. Here, again, thepaint is charged and is later fully dispersed through the action of theair moving means.

While the embodiments of the present invention. as herein disclosed,constitute preferred forms, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. An apparatus for electrostaticaily depositing paint on an article tobe painted comprising in combination, a source of electrostatic powerhaving one pole thereof attached to the article to be painted, ahorizontally disposed stationary paint distributor spaced from thearticle and attached to the other pole of said power source, means forsupplying paint to the distributor and for causing flow of the paintfrom the distributor whereby the said paint carries an electrostaticcharge similar to the charge on the distributor, an air moving meanscomprising a squirrel cage blower rotating on an axis substantiallyconcentric with the distributor and surrounding the paint beingdischarged therefrom for throwing the charged paint outwardly thereof indispersed condition in a plane substantially normal to the axis ofrotation of said means, and a second, auxiliary air moving meanscomprising a plurality of compressed air jets substantially concentricwith the first mentioned air moving means for supplying additional airwithin said first air moving means for aiding in the mechanicaldispersion of paint therefrom.

2. An apparatus for electrostatically depositing paint on an article tobe painted comprising in combination, a source of electrostatic powerhaving one pole thereof at- 5 tached to the article to be painted, ahorizontally disposed stationary paint distributor spaced from thearticle and attached to the other pole of said power source, means forsupplying paint to the distributor and for causing flow of the paintfrom the distributor whereby the said paint carries an electrostaticcharge similar to the charge on the distributor, an air moving meansrotating on an axis substantially concentric with the distributor andsurrounding the paint being discharged therefrom for throwing thecharged paint outwardly thereof in dispersed condition in a planesubstantially normal to the axis of rotation of the said means, a secondauxiliary air moving means substan-' tially concentric with the firstmentioned air moving means for supplying additional air within saidfirst air moving means for aiding in the mechanical dispersion of painttherefrom, and a third air moving means positioned below the first airmoving means for aiding in the concentration and direction of the paintparticles discharged from the first air moving means.

References Qited by the Examiner UNITED STATES PATENTS 2,894,691 7/59Secilacsik 117-93 2,976,175 3/61 Reindl 11793 3,001,719 9/61 Sigvardsson23915 FOREIGN PATENTS 1,212,938 10/59 France.

RICHARD D. NEVIUS, Primary Examiner.

1. AN APPARATUS FOR ELECTROSTATICALLY DEPOSITING PAINT ON AN ARTICLE TOBE PAINTED COMPRISING IN COMBINATION, A SOURCE OF ELECTROSTATIC POWERHAVING ONE POLE THEREOF ATTACHED TO THE ARTICLE TO BE PAINTED, AHORIZONTALLY DISPOSED STATIONARY PAINT DISTRIBUTOR SPACED FROM THEARTICLE AND ATTACHED TO THE OTHER POLE OF SAID POWER SOURCE, MEANS FORSUPPLYING PAINT TO THE DISTRIBUTOR AND FOR CAUSING OF THE PAINT FROM THEDISTRIBUTOR WHEREBY THE SAID PAINT CARRIES AN ELECTROSTATIC CHARGESIMILAR TO THE CHARGE ON THE DISTRIBUTOR, AN AIR MOVING MEANS COMPRISINGA SQUIRREL CAGE BLOWER ROTATING ON AN AXIS SUBSTANTIALLY CONCENTRIC WITHTHE DISTRIBUTOR AND SURROUNDING THE PAINT BEING DISCHARGED THEREFROM FORTHROWING THE CHARGED PAINT OUTWARDLY THEREOF IN DISPERSED CONDITION IN APLANE SUBSTANTIALLY NORMAL TO THE AXIS OF ROTATION OF SAID MEANS, AND ASECOND, AUXILIARY AIR MOVING MEANS COMPRISING A PLURALITY OF COMPRESSEDAIR JETS SUBSTANTIALLY CONCENTRIC WITH THE FIRST MENTIONED AIR MOVINGMEANS FOR SUPPLYING ADDITIONAL AIR WITHIN SAID FIRST AIR MOVING MEANSFOR AIDING IN THE MECHANICAL DISPERSION OF PAINT THEREFROM.